U.S. Pat. No. 6,808,337 B1 discloses a maritime vessel with a stationary crane mounted thereon. The crane comprises a counterweight in order to counterbalance external and internal moments resulting from a load moment and to prevent tipping of the crane. A maritime vessel 1 according to the prior art is illustrated in FIG. 1, 2. A crane 2 is provided stationary on the vessel 1. The crane 2 comprises a founding structure 3 as a tower structure, a coupling unit 4 as a slewing ring and a superstructure 5 which is coupled to the founding structure 3 utilizing the coupling unit 4. The superstructure 5 comprises a base crane structure 6 which is directly connected via the coupling unit 4 to the founding structure 3. The superstructure 5 is slewably coupled to the founding structure 3 around a vertical axis 7. The superstructure 5, the coupling unit 4 and the founding structure 3 are coaxially aligned with the vertical axis 7. The superstructure 5 further comprises a main boom 8 and a derrick mast 9. The derrick mast 9 is also called superlift (SL) mast. The main boom 8 is pivotally hinged at a first end to the base crane structure 6. The derrick mast 9 is pivotally hinged at a first end to the base crane structure 6. The crane 2 enables lifting, holding and lowering a load 10 that is carried at a second end of the main boom 8. The main boom 8 is connected to the derrick mast 9 via a main stay 11. At a second end 12 of the derrick mast 9 a pendant 13 is provided for suspending a superlift counterweight 14. Further, the base crane structure 6 carries at least two superstructure counterweights 15 that are symmetrically aligned on both sides of the base crane structure 6. Further, the second end 12 of the derrick mast 9 is connected via pendants 16 to an A-frame 17 and to a boom hoist pulley 18.
U.S. Pat. No. 4,729,486 discloses a ring lift crane having a counterweight being radially displaceable connected to a base crane concerning a vertical slewing axis. In order to reduce an effective amount of the counterweight required for a safe operation of the crane, it is known from an article “Sarens goes to sea”, dated Aug. 13, 2008 published in the magazine “Cranes today” to connect cables in order to detour the superlift counterweight forces away from the crane. Such connection cables are fixed to lugs welded onto the deck of a barge. US 2005/0211651 A1 discloses a stationary system for reducing the counterweight that needs to stay on a crane, whereby a derrick mast is connected via a connection cable directly to a stationary basement.
It is disadvantageous to the operation of a crane if it is either unflexible in its configuration thus its geometry due to tied down connection cables or if the overall crane structure itself becomes heavy due to the requirement to provide sufficient on board counterweight.